appendTo set to body breaks arrow keys on all unrelated input fields

Minimal issue for reproduction: https://stackblitz.com/edit/typescript-y8kult

Your Environment

• flatpickr version used: 4.6.9
• Browser name and version: Current Chrome/FF, version does not matter.

Steps to reproduce

• Set appendTo to any outer container such as body
• Have another input field on the page
• Try to use the arrow keys on that unrelated field

Arrow key usage will be blocked on the unrelated field, even though it is not related to the flatpickr input nor is flatpickr opened.

This is due to the keydown listener working on body and the isCalendarElem function checking simply for a node contains in https://github.com/flatpickr/flatpickr/blob/d4fb3a84e22de095c46a70e63e60a44c8f25eb73/src/index.ts#L1649. In turn, this causes all keydown keyCodes to receive preventDefault and thus breaking their normal operation.

This is likely fixed by https://github.com/flatpickr/flatpickr/pull/2329

[chmln]

@oliverguenther yes, this week for sure

[oliverguenther]

For anyone needing a workaround for this fix, my colleague @aleixsuau found out that removing appendTo=body has the same effect but does not trigger this bug.